latent heat | Definition, Examples, & Facts | Britannica

The latent heat associated with melting a solid or freezing a liquid is called the heat of fusion; ... For example, when a pot of water is kept boiling, latentheat TableofContents latentheat Introduction FastFacts 2-MinSummary Facts&RelatedContent Media Images More MoreArticlesOnThisTopic Contributors ArticleHistory Home Science Physics Matter&Energy latentheat physics Actions Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/science/latent-heat GiveFeedback ExternalWebsites Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). FeedbackType Selectatype(Required) FactualCorrection Spelling/GrammarCorrection LinkCorrection AdditionalInformation Other YourFeedback SubmitFeedback Thankyouforyourfeedback Oureditorswillreviewwhatyou’vesubmittedanddeterminewhethertorevisethearticle. JoinBritannica'sPublishingPartnerProgramandourcommunityofexpertstogainaglobalaudienceforyourwork! ExternalWebsites InternationalCommissionontheHistoryofMeteorology-TheDiscoveryofLatentHeat250Yearsago Print Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/science/latent-heat Feedback ExternalWebsites Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). FeedbackType Selectatype(Required) FactualCorrection Spelling/GrammarCorrection LinkCorrection AdditionalInformation Other YourFeedback SubmitFeedback Thankyouforyourfeedback Oureditorswillreviewwhatyou’vesubmittedanddeterminewhethertorevisethearticle. JoinBritannica'sPublishingPartnerProgramandourcommunityofexpertstogainaglobalaudienceforyourwork! ExternalWebsites InternationalCommissionontheHistoryofMeteorology-TheDiscoveryofLatentHeat250Yearsago By TheEditorsofEncyclopaediaBritannica • EditHistory TableofContents meltingicecubes Seeallmedia KeyPeople: JosephBlack ...(Showmore) RelatedTopics: heat heatofvaporization heatofsublimation Clausius-Clapeyronequation heatoffusion ...(Showmore) Seeallrelatedcontent→ Summary Readabriefsummaryofthistopic latentheat,energyabsorbedorreleasedbyasubstanceduringachangeinitsphysicalstate(phase)thatoccurswithoutchangingitstemperature.Thelatentheatassociatedwithmeltingasolidorfreezingaliquidiscalledtheheatoffusion;thatassociatedwithvaporizingaliquidorasolidorcondensingavapouriscalledtheheatofvaporization.Thelatentheatisnormallyexpressedastheamountofheat(inunitsofjoulesorcalories)permoleorunitmassofthesubstanceundergoingachangeofstate.Forexample,whenapotofwateriskeptboiling,thetemperatureremainsat100°C(212°F)untilthelastdropevaporates,becausealltheheatbeingaddedtotheliquidisabsorbedaslatentheatofvaporizationandcarriedawaybytheescapingvapourmolecules.Similarly,whileicemelts,itremainsat0°C(32°F),andtheliquidwaterthatisformedwiththelatentheatoffusionisalsoat0°C.Theheatoffusionforwaterat0°Cisapproximately334joules(79.7calories)pergram,andtheheatofvaporizationat100°Cisabout2,230joules(533calories)pergram.Becausetheheatofvaporizationissolarge,steamcarriesagreatdealofthermalenergythatisreleasedwhenitcondenses,makingwateranexcellentworkingfluidforheatengines.Latentheatarisesfromtheworkrequiredtoovercometheforcesthatholdtogetheratomsormoleculesinamaterial.Theregularstructureofacrystallinesolidismaintainedbyforcesofattractionamongitsindividualatoms,whichoscillateslightlyabouttheiraveragepositionsinthecrystallattice.Asthetemperatureincreases,thesemotionsbecomeincreasinglyviolentuntil,atthemeltingpoint,theattractiveforcesarenolongersufficienttomaintainthestabilityofthecrystallattice.However,additionalheat(thelatentheatoffusion)mustbeadded(atconstanttemperature)inordertoaccomplishthetransitiontotheevenmore-disorderedliquidstate,inwhichtheindividualparticlesarenolongerheldinfixedlatticepositionsbutarefreetomoveaboutthroughtheliquid.Aliquiddiffersfromagasinthattheforcesofattractionbetweentheparticlesarestillsufficienttomaintainalong-rangeorderthatendowstheliquidwithadegreeofcohesion.Asthetemperaturefurtherincreases,asecondtransitionpoint(theboilingpoint)isreachedwherethelong-rangeorderbecomesunstablerelativetothelargelyindependentmotionsoftheparticlesinthemuchlargervolumeoccupiedbyavapourorgas.Onceagain,additionalheat(thelatentheatofvaporization)mustbeaddedtobreakthelong-rangeorderoftheliquidandaccomplishthetransitiontothelargelydisorderedgaseousstate. NewfromBritannica Thesmellassociatedwithrainfalliscalledpetrichor;themoisturecausesbacteriaindryearthtoreleaseamoleculethathumannosesareverysensitiveto. SeeAllGoodFacts Latentheatisassociatedwithprocessesotherthanchangesamongthesolid,liquid,andvapourphasesofasinglesubstance.Manysolidsexistindifferentcrystallinemodifications,andthetransitionsbetweenthesegenerallyinvolveabsorptionorevolutionoflatentheat.Theprocessofdissolvingonesubstanceinanotherofteninvolvesheat;ifthesolutionprocessisastrictlyphysicalchange,theheatisalatentheat.Sometimes,however,theprocessisaccompaniedbyachemicalchange,andpartoftheheatisthatassociatedwiththechemicalreaction.Seealsomelting.TheEditorsofEncyclopaediaBritannicaThisarticlewasmostrecentlyrevisedandupdatedbyAmyMcKenna.